Shooting 702p60 and editing it at 30p to give you half speed should work fairly well for you, I use this myself (except with 50 and 25 fps) for slow-motion replays of goals scored by the football (soccer) team I film. It would be nice to have a camera that shot at 120fps, but until the Red Scarlet comes out and I can upgrade to that, I'm "stuck" with double speed filming... ;-)

A bit of a clarification: just dropping 60P footage into a 30P timeline doesn't NECESSARILY slow your media down. For example, in Final Cut Pro, 60P footage in a 30P timeline plays regular speed. If you change the speed using the Speed tool, it doubles frames (unless you enable frame blending which then BLENDS frames but doesn't use all the 60P media frames).

BUT, if you use Cinema Tools to remap the 60P footage to 30P and place that in a 30P timeline, it uses each frame for apparent slow motion.

Depending on your editing tool, you may need to do some tomfoolery to get the exact effect (using ALL the frames) you are looking for.